1. Technical Field
This invention relates to devices employed for the shielding of a stream of molten metal from the surrounding air to prevent contamination of the molten metal stream including the use of inert gas within such shielding to help maintain the required atmosphere.
2. Description of Prior Art
Prior Art devices of this type have relied on a variety of different structures all of which isolate the molten metal stream from the atmosphere using combinations of refractory sleeves, metal jackets and inert gas infusion, see for example U.S. Pat. Nos. 4,730,812, 4,589,465, 3,749,387 and 4,555,050.
In U.S. Pat. No. 3,749,387 a method and device for shrouding a stream of molten metal utilizing a extended tube nozzle and a shroud plate is disclosed. The shroud plate having a refractory insert in a steel form with a graphite lubricating ring. The graphite ring is required to provide lubrication of the tube nozzle as the shroud plate oscillates within the mold.
U.S. Pat. No. 4,555,050 discloses a closure mechanism with a gas seal for a conical discharge nozzle with a shielding tube extending over the exterior of the nozzle forming a snug conical joint between the shielding tube and corresponding conical nozzle.
In U.S. Pat. No. 4,589,465 a top pour shroud is disclosed which provides a protective gas shroud around the molten metal stream by use of a plenum box extending from the sliding gate with a telescopically positioned hood thereoer having a skirt flange on the bottom.
U.S. Pat. No. 4,730,812 is drawn to a shielding apparatus for a molten metal stream which includes a discharge sleeve registrably engaged within the shroud having a refractory sleeve in a metal shell with a plurality of radially disposed channels within for the dispensing of gas under pressure to form an argon gas shield below the conical end of the discharge sleeve.